Semiconductor pressure sensors are known in the art.
U.S. Pat. No. 4,672,411 (Hitachi) discloses a pressure sensor (shown in FIG. 1) having a diaphragm formed in a semiconductor body, the diaphragm having a pair of pressure sensing semiconductor strips in a major surface thereof (vertical piezo-resistive strips 30, 31 in FIG. 1). Each of the strips 30, 31 is connected at one end to the other one by a semiconductor region (triangular region 32 in FIG. 1). The semiconductor region 32 is formed in a direction of small piezo-resistive coefficients, while the strips 30, 31 are formed in a direction of large piezo-resistive coefficients. The semiconductor region 32 (triangle) has a smaller sheet resistance than the resistance of the strips 30, 31. Also, electrode lead-out regions are provided at the other ends of the strips 30, 31, which regions have low resistance, extend in a direction of small piezo-resistive coefficients, and extend beyond the edge of the diaphragm so the electrodes contact the semiconductor body outside the diaphragm. The resistive strips 30, 31 are connected in a Wheatstone bridge. Deformation of the diaphragm causes the diffused resistor layers (i.e. the piezo-resistive strips) to expand or shrink so as to change their resistances. The pressure sensor senses a pressure change by electrically detecting the change of the resistances.
However, this pressure sensor is not very accurate in all circumstances, e.g. in case of temperature fluctuations, and in case of residual package-stress.